Learn core animation the hard way

###Document

1. CABasicAnimation Keypath
2. Animation Types and Timing Programming Guide
3. CGAffineTransform
4. Quartz 2D Programming Guide
5. 放射变换
6. 组合动画
7. http://www.cnblogs.com/v2m_/archive/2013/05/09/3070187.html
8. 几个常用动画代码